In the related art, sorting machines for selecting grains such as rice and soybeans, resin pellets, coffee beans, and other granular target objects based on the predetermined criteria such as color and size are known.
The sorting machines may selectively removing mixed-in the unexpected foreign material (see Patent Document 1 below).
The sorting machine may pour the target objects into an inclined chute from above position to be dropped through the chute. The one or a pair of optical units positioned across the downward trajectory in the sorting machine may capture images of the granular objects while their falling. Based on an inspection result of the optical unit, target objects that are determined to be foreign materials or outside the criteria are conveyed by the force of the air ejected from an ejector nozzle to a storage tank separate from the storage tank in which target objects within the criteria are dropped and stored. This also applies for target objects on a conveyor, and objects that the optical unit detects as foreign materials or outside the criteria are conveyed by the another conveyor so as to be distinguishable from the target objects within the criteria.
In addition, a granular object sorting device is disclosed, in which light from a measurement target region is reflected by a reflector, the optical pass is bent by another reflector, and the bended light is received at a light-receiving device (see Patent Document 2 below).